A Study On Key Technology And Solid State Frequency Doubler Of Terahertz Detector Front-End

Terahertz(THz)technology is a new frontal and interdisciplinary discipline,which has been widely used in many fields such as astronomical exploration.THz detectors using in astronomical observations can be divided generally into two types of coherent and non-coherent detectors.A study on the key passive components like filters is one of the important areas in this field.In addition,the THz solid-state frequency multiplier is also one of the important components in the coherent receiver.This dissertation focuses on the in-depth research of several key passive technologies and the solid-state frequency doubler of the detector front-end based on the background application of THz astronomical detectors.The main work and achievements in this dissertation are as follows:1.Terahertz low-loss rectangular waveguide bandpass filters with quasi-elliptical response.In order to solve the existing problems of the difficult machining and poor performance,four types of waveguide filters with high performance are proposed in THz band.They can help to select the desired band and improve the proformance of the detectors for the continuous spectrum observations.Firstly,a W-band 4-order quasi-elliptic waveguide filter is proposed.A simple filter construction,which can be fabricated by numerical control(CNC)technology easily,is achieved.While the high performance of frequency selective,out-of-band rejection and four transmission zeros are obtained in this W-band filter.Secondly,such design is simplified and extended to the 220 GHz.The characteristic with very low-loss of 0.6 dB is achieved based on CNC and gold-plated technique.And the effect of the process error on the filter performance is analized systematically.Finally,two types of 260 GHz quasi-elliptical waveguide filters are presented based on the high-order mode resonance.The introduction of the large high-order mode resonance cavity structure can not only be used to implement superior selective and rejection performance,but can also reduce the processing difficulty of high frequency waveguide structure.Thus low insertion loss of 0.7 and 0.5 dB are acquired in such high frequency waveguide filter.2.Terahertz wideband ridged waveguide bandpass filter and diplexer.It is difficult to realize wideband waveguide devices in THz band based on the conventional rectangular waveguides due to the limited fundamental mode frequency range.To solve this problems,the ridged waveguide structure is first expanded to be used at THz frequencies in this dissertation.A 240 GHz frequency ridged waveguide bandpass filter with wideband of 50%and a wideband diplexer with two passband of 180?300 GHz and 300?420 GHz are designed and manufactured based on the micro-electro-mechanical system(MEMS)technology.Finally,a quasi optical testing system based on the THz high sensitive supercondocting mixer is set up to implement the measurement of the 240 GHz ridged waveguide filter.The measured results are consistent with the simulations.3.Terahertz beaming enhancing technology based on the metal and dielectric film loading periodic structures.THz components usually exist problems of poor efficiency,high loss,low gain,etc.In order to improve their properties,a metal film loading periodic circular grooves structure(Bull's-eye structure)and a dielectric thin film loading periodic metal elliptic rings structure at 500 GHz frequency are presented in this dissertation.The MEMS process,laser technology and sputtering gold technique are carried out for the device fabrication.Finally,the THz beam vertical collimation and enhanced radiation characteristics are achieved.In addition,the effects of both structures loading with different cycles and shapes on the beam radiation characteristic are analyzed in detail,which would provide the basis for the design and application of the loading periodic structures on THz functional devices.4.Terahertz wideband and high efficiency frequency doubler based on GaAs Schottky diodes.The good performance of wideband,high conversion efficiency,high power capacity and robust output power is always the developmental goal of the THz frequency multipliers.In this thesis,accurate nonlinear and 3-D electromagnetic models of the GaAs Schottky diode are builded firstly based on the advanced LERMA-C2N Schottky process.Then six Schottky diodes with large anode contact structure,broadband probe coupling,novel low-pass filter with high rejection,multi-stage matching waveguide structures are adoted to design the high performance 300 GHz doubler.The measured results exhibit that very good performance of high power capacity(>60 mW),high power output(?10 mW),high conversion efficiency(>16%)and wideband(24%)are delivered in this 300 GHz doubler.Finally,the design and implementation of the 300 GHz power-combined frequency doubler is presented.